Taken from
https://github.com/qvint/ungoogled-chromium-fedora/commit/a68fdd679566da5134d916776f14e00c8e6a8042

--- a/chrome/tools/convert_dict/convert_dict.cc
+++ b/chrome/tools/convert_dict/convert_dict.cc
@@ -24,6 +24,7 @@
 #include "build/build_config.h"
 #include "chrome/tools/convert_dict/aff_reader.h"
 #include "chrome/tools/convert_dict/dic_reader.h"
+#include "components/spellcheck/common/spellcheck_common.h"
 #include "third_party/hunspell/google/bdict_reader.h"
 #include "third_party/hunspell/google/bdict_writer.h"
 
@@ -76,13 +77,32 @@ bool VerifyWords(const convert_dict::Dic
 }
 
 int PrintHelp() {
-  printf("Usage: convert_dict <dicfile base name>\n\n");
-  printf("Example:\n");
-  printf("  convert_dict en-US\nwill read en-US.dic, en-US.dic_delta, and "
-         "en-US.aff from the current directory and generate en-US.bdic\n\n");
+  printf(
+      "Usage:\n"
+      "  dict-utility list\n"
+      "  dict-utility convert <aff_path> <dic_path> <out_path>\n");
   return 1;
 }
 
+int PrintList() {
+  base::FilePath root("/");
+  std::vector<std::string> languages = spellcheck::SpellCheckLanguages();
+
+  for (auto &language : languages) {
+    std::string language_region =
+        spellcheck::GetSpellCheckLanguageRegion(language);
+    base::FilePath language_bdic_path =
+        spellcheck::GetVersionedFileName(language, root).BaseName();
+
+    printf("%s\t%s\t%s\n",
+        language.c_str(),
+        language_region.c_str(),
+        language_bdic_path.value().c_str());
+  }
+
+  return 0;
+}
+
 }  // namespace
 
 #if defined(OS_WIN)
@@ -91,16 +111,15 @@ int wmain(int argc, wchar_t* argv[]) {
 int main(int argc, char* argv[]) {
 #endif
   base::EnableTerminationOnHeapCorruption();
-  if (argc != 2)
+  if (argc == 2 && strcmp(argv[1], "list") == 0)
+    return PrintList();
+  if (argc != 5 || strcmp(argv[1], "convert") != 0)
     return PrintHelp();
 
   base::AtExitManager exit_manager;
   base::i18n::InitializeICU();
 
-  base::FilePath file_base = base::FilePath(argv[1]);
-
-  base::FilePath aff_path =
-      file_base.ReplaceExtension(FILE_PATH_LITERAL(".aff"));
+  base::FilePath aff_path = base::FilePath(argv[2]);
   printf("Reading %" PRFilePath " ...\n", aff_path.value().c_str());
   convert_dict::AffReader aff_reader(aff_path);
   if (!aff_reader.Read()) {
@@ -108,8 +127,7 @@ int main(int argc, char* argv[]) {
     return 1;
   }
 
-  base::FilePath dic_path =
-      file_base.ReplaceExtension(FILE_PATH_LITERAL(".dic"));
+  base::FilePath dic_path = base::FilePath(argv[3]);
   printf("Reading %" PRFilePath " ...\n", dic_path.value().c_str());
   // DicReader will also read the .dic_delta file.
   convert_dict::DicReader dic_reader(dic_path);
@@ -135,8 +153,7 @@ int main(int argc, char* argv[]) {
     return 1;
   }
 
-  base::FilePath out_path =
-      file_base.ReplaceExtension(FILE_PATH_LITERAL(".bdic"));
+  base::FilePath out_path = base::FilePath(argv[4]);
   printf("Writing %" PRFilePath " ...\n", out_path.value().c_str());
   FILE* out_file = base::OpenFile(out_path, "wb");
   if (!out_file) {
--- a/chrome/tools/convert_dict/BUILD.gn
+++ b/chrome/tools/convert_dict/BUILD.gn
@@ -34,6 +34,7 @@ executable("convert_dict") {
     "//base",
     "//base:i18n",
     "//build/win:default_exe_manifest",
+    "//components/spellcheck/common",
     "//third_party/hunspell",
   ]
 }
--- a/components/spellcheck/common/spellcheck_common.h
+++ b/components/spellcheck/common/spellcheck_common.h
@@ -30,6 +30,8 @@ static const size_t kMaxSyncableDictiona
 // chrome/browser/resources/settings/languages_page/edit_dictionary_page.js
 static const size_t kMaxCustomDictionaryWordBytes = 99;
 
+std::string GetSpellCheckLanguageRegion(base::StringPiece input_language);
+
 base::FilePath GetVersionedFileName(base::StringPiece input_language,
                                     const base::FilePath& dict_dir);